This invention relates generally to injection molding and more particularly to a method of manufacturing an injection molding heated melt distribution manifold having a melt passage extending therethrough with a number of elbows.
Making multi-cavity injection molding systems having a steel melt distribution manifold with an integral electrical heating element in which the melt passage branches to a number of outlets is well known in the art. These manifolds are made with the melt passage having at least one lateral portion branching out to a pair of elbows leading to outlet bores extending to the front face of the manifold. Previously, these manifolds having a melt passage with elbows have been made by cross drilling bores and plugging them off and by machining matching grooves in two plates and brazing them together. Both of these methods are seen in U.S. Pat. No. 4,648,546 to Gellert which issued Mar. 10, 1987. It is also known to preform each elbow in a plug and then simultaneously braze the heating element in a channel and the plug in a bore extending from an end of the manifold. This is shown in U.S. Pat. No. 4,609,138 to Harrison which issued Sep. 2, 1986. Similarly, it is shown in European Patent Publication Number 0 523 549 A2 to Gellert et al. published Jan. 20, 1993 to preform melt passage elbows in inserts or plugs removably seated in openings extending from the front face of a manifold.
While the manifolds made by these previous methods are satisfactory for many applications, they have the disadvantage that they are too time consuming and costly.